The present invention relates to a paging receiver having a circuit for flashing a light emitting element and, more particularly, to a paging receiver having a circuit for selectively flashing a plurality of light emitting elements.
A current trend in the radio paging art is toward a paging receiver or pager operable with a plurality of paging numbers and/or, to promote the use of the receiver in multiple locations, with a plurality of receive frequencies. In parallel with such a trend, means for alerting a person who carries a pager to the reception of a call and means for allowing the person to confirm a receive frequency being set have been proposed in a variety of forms. For example, alerting means which assigns a different tone or a light emitting element of a different color to each paging number is available. Also available is frequency confirming means which, when a person selects a particular receive frequency which matches a particular location, displays that frequency by causing a light emitting element of a particular color to flash.
The light emitting element used with the above-described type of alerting means or frequency confirming means is usually implemented by a light emitting diode (LED). While about 2-volt power supply is needed to turn on an LED, a 1-volt battery which is easy to replace is adopted in practice for powering an LED because a pager is usually carried by a person. It is therefore necessary to install in a pager a circuit for causing an LED to flash by boosting the output of the 1-volt battery.
An example of a circuit for flashing an LED as stated above is disclosed in Japanese Laid-Open Utility Model Publication (Kokai) No. 57-39156. The circuit shown and described in this Utility Model Publication includes a 1-volt battery and a coil which is connected in parallel with an LED. Energy generated by the 1-volt battery is charged in the coil and then discharged so that the resulting counter electromotive force causes the LED to glow. Such a procedure is repeated to turn on and off the LED periodically.
An attempt to implement a flashing circuit having a plurality of LEDs of different colors by the above-described technique would result in the need for the same number of flashing circuits as the number of LEDs. More specifically, when a flashing circuit using the same number of prior art circuits as the number of LEDs is simply applied to a pager, a prohibitive number of circuit parts are needed, especially the same number of boosting coils as the number of LEDs are required. Such numerous circuit parts obstruct the miniaturization of the pager. What impedes the miniaturization most is the large contour of the coil which is unavoidable in guaranteeing inductance necessary for boosting. Increasing the number of boosting coils in proportion to the number of LEDs would add to the overall size of a pager. This is also true with a case wherein a plurality of prior art flashing circuits are applied to the alerting means of a small-size receiver which is powered by a DC power supply.